In a semiconductor manufacturing process, a plasma processing apparatus configured to perform a plasma process in order to deposit or etch a thin film has been widely employed. As an example of such a plasma processing apparatus, there is known a plasma CVD (Chemical Vapor Deposition) apparatus configured to deposit a thin film or a plasma etching apparatus configured to perform an etching process.
The plasma processing apparatus includes, for example, a chamber in which a plasma process is performed on a processing target object, a gas exhaust unit configured to depressurize the inside of the chamber, a gas supply unit configured to supply a processing gas into the chamber, and so forth. Further, the plasma processing apparatus also includes a plasma generation device configured to supply electromagnetic energy such as a microwave or a RF wave in order to excite a processing gas in the chamber into plasma; and a bias voltage application device configured to apply a bias voltage and accelerate ions in the plasma toward the processing target object placed within the chamber.
In the plasma processing apparatus, when etching a processing target object on which an insulating film for dual damascene wiring is formed, there is known a technique of forming a mask having plasma resistance on a surface of the insulating film to form an etching pattern on the insulating film. For example, it is described in Patent Document 1 that a Ti-containing film (e.g., a TiN film) having a preset pattern is formed on a surface of an insulating film of a processing target object and the insulating film on the processing target object is etched by using the TiN film as a mask.
Patent Document 1: Japanese Patent Laid-open Publication No. 2006-216964
In this conventional method, however, there has been a risk of degrading etching characteristics with a lapse of time due to a Ti-containing film adhering to the inside of the chamber. That is, in the convention method, not only the insulating film but also the TiN film itself may be etched when the insulating film on the processing target objet is etched by using the TiN film as a mask. Accordingly, in the conventional method, the Ti-containing film originated from the etched TiN film may adhere to various components within the chamber, so that plasma density fluctuates within the chamber. As a result, the etching characteristics of the processing target object may be degraded as time passes by. This degradation of the etching characteristics may become remarkable when processing multiple lots of processing target objects.